In '623, the disclosure of which is incorporated herein by reference, a special alloy is described as being particularly useful under high temperature/oxidizing conditions such as encountered by furnace rollers in ceramic tile industry frit-firing applications. The '623 alloy, generally speaking, contains about 19 to 28% chromium, about 55 to 65% nickel, about 0.75 to 2% aluminum, about 0.2 to 1% titanium, up to about 1% each of silicon, molybdenum, manganese and niobium, up to about 0.1% carbon, about 0.04 to 0.1% nitrogen, up to about 0.01% boron, with the balance being essential iron. A preferred composition contains 21 to 25% chromium, 58 to 63% nickel, 1 to 2% aluminum, 0.3 to 0.7% titanium, 0.1 to 0.6% silicon, 0.1 to 0.8% molybdenum, up to 0.6% manganese, up to 0.4% niobium, 0.02 to 0.1% carbon, and 0.04 to 0.08% nitrogen, the balance being essentially iron.
Notwithstanding the attributes of the '623 alloy, improvement in respect of the manufacture thereof is desirable in an effort to reduce cost. Apparently, the desired titanium nitride phase that forms tends to float during the melting process. This flotation renders electroslag remelting difficult particularly where about 0.04% or more nitrogen is a desideratum. Moreover, the tendency of the TiN to segregate to the top of the cast ingots rendered some ingots too inhomogeneous. This causes grinding loses depending on the amount of TiN formed. Too, where the aluminum content significantly exceeded the percentage of titanium, the alloy tended to form AlN such that the amount of free aluminum was depleted whereby it was not available for enhancing oxidation resistance. Furthermore, while titanium was necessary to impart grain-stabilization by reason of the TiN phase (and to minimize AlN formation) it has been observed that excessive titanium detracts from oxidation resistance.